Question

Do you drink water that's been left sitting out overnight or even for another day? Have you noticed it tastes different?

Tap water that has been left to sit out slowly begins to acquire(获得) off taste. Many people think that this is because of microorganisms. But that's not what makes old water taste not fresh. For that we can thank carbon dioxide. After about 12 hours, tap water starts to go flat as carbon dioxide in the air starts to mix with the water in the glass, lowering its PH and giving it an off taste. But it's most likely safe to drink.

However, back to those microorganisms. If you use a dirty glass day after day, there is more of a chance of bacteria making themselves known; a risk that increases if you share the glass with another mouth as well. But assuming(假设) you use a fresh glass every few days, you probably won't have a problem unless the glass has been touched by dirty fingers, and especially if those dirty fingers went unwashed after using the bathroom.[

As for plastic water bottles that have been left out in the sun or in the car, step away from the bottle, warns Dr. Kellogg Schwab, director of the Johns Hopkins University Water Institute. "A chemical called biphenyl-A, or BPA, along with other things used to make plastic can leach(过滤) into your water if the bottle heats up or sits in the sun," he explains. BPA, as you probably know, has been linked to everything from heart disease to cancer. Schwab also adds that plastic used for commercial bottled water isn't meant to be washed or refilled, so use only one time and recycle. Or don't buy them at all; use refillable water bottles instead.

1.Tap water begin to acquire an off taste because of______ .

A. carbon dioxide    B. BPA

C. the glass    D. the microorganism

2.According to Paragraph 2, tap water that's been left sitting out for 12 hours____.

A. contains few microorganisms    B. is still safe to drink

C. tastes better    D. is most likely undrinkable

3.What should we do with plastic water bottles that have been left out in the sun or in the car?

A. Use them after they cool down.

B. Clean them and use them again.[来

C. Throw them away.

D. Refill them with fresh water

4.Which of the following is true about BPA?

A. It is safe for people to use.

B. It is a kind of new material.

C. It is the main material to make plastic.

D. It can cause great harm to people.

Answer

1.A

2.B

3.C

4.D

【解析】本文是一篇说明文。介绍了隔夜后的水变味的原因以及应对方法。

1.细节理解题。根据“After about 12 hours, tap water starts to go flat as carbon dioxide in the air starts to mix with the water in the glass, lowering its PH and giving it an off taste.”大约12小时后，空气中的二氧化碳开始与杯中的自来水混合，使它的味道变淡，PH值降低，可知成因是二氧化碳。故选A。

2.细节理解题。根据“But it's most likely safe to drink.”但它喝起来还是安全的，故选B。

3.细节理解题。根据“As for plastic water bottles that have been left out in the sun or in the car, step away from the bottle.”至于被留在太阳下或车里的塑料水瓶，离它们远点，可知它们是有害的。故选C。

4.细节理解题。根据“BPA, as you probably know, has been linked to everything from heart disease to cancer.”你大概知道，BPA被和心脏病、癌症等联系起来，可知BPA对人体有害。故选D。